The problem of the sign of the size correction to the surface energy per unite area of a single charged metal nanocluster within the liquid-drop model (LDM) is considered. Within the stabilized jelly model detailing the LDM, the effective radii of the electron cloud for Cs, Na, Mg and Al clusters are estimated from the asymptotic behaviour of the electrical capacitance calculated by the Kohn–Sham method. The uncertainty of the cluster boundary associated with the atomic-scale roughness and nonsphericity of the surface, with taking into account the effective radius of the electron cloud of the cluster, can lead to an inversion of the sign of the size correction for surface tension. The distribution function of Cs clusters by charge and number of atoms in dense vapour on the saturation line is estimated. The fact that the surface energy of a metal depends on the dielectric constant as weighted average over the area of contact with the external environment is discussed. A metal droplet on a dielectric substrate and a droplet in its own dense vapour are discussed as appropriate contacts. The dependence of surface tension on electrical capacitance for Cs, Na, Mg, Pb, Au and Al is calculated. Contact of a droplet with a dielectric substrate always leads to a decrease in surface energy.